# A skateboarder starts from rest at the top of a slope. She rolls down the slope, reaching a speed of 8 m/s after 4 seconds of uniform acceleration. She then travels along a flat section of track at a constant speed of 8 m/s for 10 seconds before gradually decelerating to a stop. Describe the motion of the skateboarder in each of the three stages of her journey, and explain what the constant speed stage tells us about the forces acting on the skateboarder during that stage.

> Edexcel A-Level Physics (9PH0) — 2.1 Motion · Describe · 5 marks

## Mark scheme (5 marks)

1. Stage 1: the skateboarder accelerates uniformly (from rest / starting at 0 m/s, reaching 8 m/s in 4 s)
2. Stage 2: the skateboarder travels at constant/steady speed (8 m/s for 10 s)
3. Stage 3: the skateboarder decelerates (speed decreases / slows down to a stop)
4. At constant speed, the forces on the skateboarder are balanced / the resultant force is zero
5. Because there is no resultant force, there is no acceleration (Newton's First Law / an object at constant velocity has zero resultant force)

## Key terms

- [uniform acceleration](https://www.gradenine.co.uk/glossary/uniform-acceleration)
- [constant speed](https://www.gradenine.co.uk/glossary/constant-speed)

## Related

- [Revision notes for Edexcel A-Level Physics (9PH0)](https://www.gradenine.co.uk/learn)
- [How to answer "Describe" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

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Source: [GradeNine](https://www.gradenine.co.uk/q/a-skateboarder-starts-from-rest-at-71d66d69) · Published by Druglandscape Ltd.